1. Technical Field
The invention relates to sliding bearings having a depository surface having at least one depository, which is a sliding surface and/or a surface of an oil supply groove, the depository being a recess open towards the depository surface and having a depository wall extending from the depository surface in the direction towards the bearing back.
2. Related Art
The sliding surfaces of sliding bearings are profiled for various reasons. For example, in DE 39 05 450 C2 it was proposed to provide sliding bearings with grooves that are filled with a soft material so that the harder material alternates with the softer material in the sliding surface in order to achieve a better wear resistance and fatigue strength.
GB 1,128,370 A describes a lubricant-free bearing in which recesses are formed in the sliding surface in the form of grooves or pockets to convey dirt particles out of the bearing. Foreign bodies that penetrate into the bearing are collected in the recesses and are transported in the direction of rotation of the shaft along the flanks of the recesses and conveyed out of the bearing at the ends of the bearing.
Sliding bearings in internal combustion engines are the subject of continuous further development. Continuously greater stress is occurring in internal combustion engines and therefore also on sliding bearings. At the same time, the size of engines is being reduced. Moreover, ever thinner oils are being used to reduce friction. This results in that the thickness of the lubricating films which prevent contact between the bearing and the shaft is constantly becoming less.
Consequently, the system is becoming more and more susceptible to unwanted external influences such as the intrusion of large dirt particles and chips for example during the manufacture of the components, which can never be completely avoided.
Furthermore, the structure of the bearing shell is changing. Lead, which has very good sliding properties, is being replaced by other elements. The stress capacity of the bearing is also being increased, and this is resulting in a greater susceptibility to external influences. Layers that withstand great stress are as a rule thinner and harder than conventional layers and this entails a lesser embeddability, i.e. the capability to embed hard particles into the sliding surface to reduce wear. By substituting lead-containing layers, the remaining slidability of a damaged layer is also reduced. This also reduces the embeddability, with the consequentially reduced operational safety of the bearing. If there is an intrusion of foreign bodies, the bearing will therefore be damaged to a greater extent than hitherto, and this can result in a total failure of the tribo-system.
Foreign particles can have various origins and reach the oil circuit in different ways. For example, dirt resulting from the manufacture of the components, such as bore chips, welding or soldering residue, residual dirt from individual components from the packaging etc., can damage the bearing. Moreover, wear particles for example from oil pumps or chain tensioners or combustion residues from agglutinated and burned hydrocarbon compounds may penetrate the bearing. In addition, foreign particles from maintenance work or contaminants in the oil when changing the oil may lead to damage to the bearing.
The foreign bodies may be several times larger than the bearing play, and therefore cannot easily be washed out of the bearing. They move in the direction of the flow of oil towards the end of the oil supply bore and the discharge of the foreign bodies is prevented by the bearing. Thus, the foreign particles are then pulled from the oil supply bore in a circumferential direction over the susceptible sliding bearing surface, thereby damaging the bearing by the formation of scoring. In extreme cases, the foreign body tries to leave the bearing in the area of least resistance, i.e. in the area of exposure (the greatest width of the gap), and is carried as a consequence of the wedge effect between the shaft and exposure by the shaft up until deep into the stressed areas of the bearing. Such damage generally leads to a complete failure of the bearing.